Discoidin Domain Receptors (DDRs) are type I transmembrane glycoproteins, which are represented by two receptors DDR1 and DDR2. DDR1 is mainly expressed in epithelial cells and DDR2 in stroma. The DDR1 subfamily includes five isoforms generated by alternative splicing with DDR1a and DDR1b as the most common isoforms and DDR1d and DDR1e being either truncated or inactive kinases, respectively. A single protein represents the DDR2 subtype. DDR1 is a collagen-activated receptor tyrosine kinase (RTK). DDR1 is widely expressed during embryonic development and in adult tissues, particularly in epithelia of skin, lung, liver, kidney, gut, colon and brain. Among the collagen-receptor families, the DDRs are the only RTKs that undergo autophosphorylation in response to various collagens.
Structurally, the ectodomain of DDRs is composed of a discoidin (DS) domain, a DS-like domain, and an extracellular juxtamembrane (EJXM) region, which are followed by a single-pass transmembrane segment. The intracellular portion of the receptor is composed of a relatively long intracellular juxtamembrane (IJXM) region and a C-terminal kinase domain (KD). DDRs display an atypical activation kinetics manifested by a slow and sustained phosphorylation, which suggests a unique mechanism of receptor activation that differentiates DDRs from other members of the RTK family. DDRs initiate signaling pathways that are critical for cell-collagen interactions and thus play key roles in many physiological and pathological conditions involving collagen remodeling [Leitinger, B., Discoidin domain receptor functions in physiological and pathological conditions. International review of cell and molecular biology, 2014. 310: p. 39-87; Hohenester, E., Signalling complexes at the cell-matrix interface. Current opinion in structural biology, 2014. 29C: p. 10-16].
Some light on the physiological function of DDR1 can be indirectly deduced by the DDR1-knockout mouse phenotype [Vogel, W. F., et al., Discoidin domain receptor 1 tyrosine kinase has an essential role in mammary gland development. Molecular and cellular biology, 2001. 21(8): p. 2906-17]. DDR1-knockout mice survived gestation but are smaller in size than control littermates showing defects in the development of certain organs, such as impaired mammary gland development, poorly calcified fibula bone, and a narrower pelvis. In addition to the above defects present in DDR1-knockout mice, mutant females are unable to lactate because of the failure of alveolar epithelium to secrete milk proteins. DDR1-null female mice during pregnancy showed hyperproliferation and aberrant differentiation of lobulo-alveolar epithelial cells. At birth, the alveoli showed intracellular lipid production and deposition but failure to secrete milk into the central lumen. In the early pubertal stage, the mammary gland development defect was manifest as a delay in mammary duct outgrowth, enlargement in primary ducts, and the terminal end buds due to a marked increase in cell proliferation rate in the mutant mice. In addition, a substantial deposition of collagen was shown in and around mammary gland epithelial cells in DDR1-knockout mice.
The DDR1-knockout adult mice exhibit proteinuria and urinary acanthocytes. Results from electron microscopy demonstrate thickening of subepithelial glomerular basement membrane as well as a focal loss of the podocyte slit diaphragms. These data suggest that the loss of cell-matrix communication in DDR1-deficient podocytes appears to result in excess accumulation of basement membrane proteins, which leads to disturbed anchorage of foot processes and disruption of the slit diaphragm. In other words, the interaction between type IV collagen and DDR1 plays an important role in maintaining the structural integrity of the glomerular basement membrane [Gross, O., et al., DDR1-deficient mice show localized subepithelial GBM thickening with focal loss of slit diaphragms and proteinuria. Kidney International, 2004. 66(1): p. 102-11].
Despite some of the developmental defects found in DDR1-null mice, these mice have been valuable in understating the role of these receptors in various diseases, including cancer, atherosclerosis, lung and liver fibrosis, renal injury, and osteoarthritis.
Many cancers are characterized by dysregulated kinome expression and activation. DDRs play a key role in cancer progression and metastatisation processes, in part by regulating the interaction of cancer cells with collagens [Valiathan, R. R., et al., Discoidin domain receptor tyrosine kinases: new players in cancer progression. Cancer metastasis reviews, 2012. 31(1-2): p. 295-321]. Both DDRs are overexpressed in a large number of different types of cancer, ranging from lung, breast, brain, esophagus, head and neck, liver, and prostate cancers to lymphomas and leukemias. Dysregulated DDR expression has been shown in a number of studies to correlate with unfavorable outcomes for patients and altered functions of DDR1 and DDR2 likely contribute to tumorigenesis. Moreover, DDR1 can confer resistance to chemotherapy and mediate prosurvival signals in breast cancer and lymphoma cell lines [Cader, F. Z., et al., The EBV oncogene LMP1 protects lymphoma cells from cell death through the collagen-mediated activation of DDR1. Blood, 2013, 122(26): p. 4237-45; Ongusaha, P. P., et al., p53 induction and activation of DDR1 kinase counteract p53-mediated apoptosis and influence p53 regulation through a positive feedback loop. The EMBO journal, 2003. 22(6): p. 1289-301] and may be involved in the recurrence of certain types of cancer [Jian, Z. X., et al., Involvement of discoidin domain 1 receptor in recurrence of hepatocellular carcinoma by genome-wide analysis. Medical oncology, 2012. 29(5): p. 3077-82]. However, the molecular mechanisms underlying the roles of the DDRs in various steps of cancer progression are largely undefined.
Screening of non-small cell lung carcinoma (NSCLC) tissue samples showed that DDR1 is significantly upregulated in these patients and that expression of DDR1 is significantly associated with overall and disease-free survival. Multivariate analysis revealed that expression of DDR1 is independent of tumor differentiation, stage, histology, and patient age. A screening for DDR mutations revealed one polymorphism with synonymous change at S495, unlikely to be of functional importance [Ford, C. E., et al., Expression and mutation analysis of the discoidin domain receptors 1 and 2 in non-small cell lung carcinoma. British journal of cancer, 2007. 96(5): p. 808-14]. Other studies underlined the relevance and role of DDR1 in metastatisation process. Screening of NSCLC samples, encompassing 86 squamous cell carcinomas, 69 adenocarcinomas, and 16 pure bronchioloalveolar carcinomas (BAC), indicated that DDR1 upregulation was more frequent in invasive adenocarcinoma (64%) compared with BAC (38%; 83). In addition, DDR1 expression was significantly correlated with lymph node metastasis in invasive NSCLC. Overexpression of DDR1 in lung cancer cells resulted in a significant increase in cell motility and invasiveness, which may correlate with the induction of matrix metalloproteinase-9 [Yang, S. H., et al., Discoidin domain receptor 1 is associated with poor prognosis of non-small cell lung carcinomas. Oncology reports, 2010. 24(2): p. 311-9; Miao, L., et al., Discoidin domain receptor 1 is associated with poor prognosis of non-small cell lung cancer and promotes cell invasion via epithelial-to-mesenchymal transition. Medical oncology, 2013. 30(3): p. 626]. These results indicate that up-regulation of DDR1 may contribute to the progression and poor prognosis of certain types of NSCLC and that this effect may be attributed to increased invasiveness.
Even if not totally understood, DDR1 seems to play a central role in modulation of inflammation and fibrosis. As fibrosis is frequently the result of an earlier inflammation event, it's not clear if the main role of DDR1 resides in the direct blockage of fibrosis processes (e.g., myofibroblast activation, collagen deposition) or more in inflammation modulation. Unfortunately, in vivo experiments performed using the DDR1 null mice do not allow to untangle these two biological processes. Modulation of fibrosis and inflammation has been demonstrated in several organs, namely lung and kidney. DDR1-deficient mice show reduced bleomycin-induced pulmonary injury characterized by reduced collagen and tenascin-C levels [Avivi-Green, C., M. Singal, and W. F. Vogel, Discoidin domain receptor 1-deficient mice are resistant to bleomycin-induced lung fibrosis. American journal of respiratory and critical care medicine, 2006. 174(4): p. 420-7]. Authors reported two possible reasons for the decreased fibrotic response in DDR1-null mice are decreased inflammation, with reduced CD3-positive lymphocytes and F4/80-positive cells infiltrating the lungs, and decreased activation of the p38 MAPK, a kinase involved in lung fibrosis. In kidney, DDR1 expression is elevated in patients with lupus nephritis and Goodpasture's syndrome as well as in a mouse model of crescentic glomerulonephritis [Kerroch, M., et al., Genetic inhibition of discoidin domain receptor 1 protects mice against crescentic glomerulonephritis. FASEB journal: official publication of the Federation of American Societies for Experimental Biology, 2012. 26(10): p. 4079-91]. Similarly, DDR1 expression increases in the glomeruli of rats that have undergone partial renal ablation [Lee, R., et al., Localization of discoidin domain receptors in rat kidney. Nephron Exp Nephrol, 2004. 97(2): p. e62-70] and in tubules of mice that have undergone unilateral ureteral obstruction [Guerrot, D., et al., Discoidin domain receptor 1 is a major mediator of inflammation and fibrosis in obstructive nephropathy. Am J Pathol, 2011. 179(1): p. 83-91]. Use of DDR1-null mice in several mouse models of kidney injury showed that compared to wild type mice DDR1-null mice have improved renal function, reduced fibrosis and reduced inflammation. In this context, DDR1-null mice are protected from angiotensin II-mediated proteinuria, glomerular fibrosis, and inflammation, and show reduced collagen deposition, tubular macrophage infiltration and pro-inflammatory cytokine levels following unilateral ureteral obstruction. Moreover, COL4A3 KO mice, the mouse model for human Alport syndrome, crossed onto the DDR1-null mice have reduced renal fibrosis and inflammation due to reduced TGF-β-mediated signaling and reduced levels of the pro-inflammatory cytokine IL6 [Gross, O., et al., Loss of collagen-receptor DDR1 delays renal fibrosis in hereditary type IV collagen disease. Matrix Biol. 29(5): p. 346-56]. Finally, DDR1-null mice have increased survival and improved renal function in a model of crescentic glomerulonephritis induced by injection of alloimmune sheep nephrotoxic serum. In that respect, finding that older DDR1-null mice show focal swelling of the glomerular basement membrane (GBM) and mild proteinuria [Gross, O., et al., DDR1-deficient mice show localized subepithelial GBM thickening with focal loss of slit diaphragms and proteinuria. Kidney Int, 2004. 66(1): p. 102-11] suggests that DDR1 might play a very different role in physiological conditions. Again, as we mentioned before in the case of the lung fibrosis, hallmark of protection conferred by DDR1 deletion in all these renal experimental studies showed reduced macrophage infiltration supporting the pro-inflammatory role of DDR1.
Despite the progress made in understanding the role of DDR1, there remains an unmet need of potent and selective compounds suitable to modulate the DDR1 receptor to treat diseases related to DDR1 overexpression. Present invention provides novel compounds which exhibit high affinity and selectivity to the DDR1 receptor and are thus suitable for the treatment or prevention of diseases related to DDR1 upregulation.